well... I don't know if I would do it that way, but there are ways you can do it, it's apparently a culinary delicacy, somewhat like caviar. Its called spherification, though that large is a bit unfeasable. You normally use Calcium alginate, rather than acetate though.

I suspect what he has done is get those water-absorbing polymer spheres you can buy from florists, they hold water into jelly like spheres, very soft, very fun to play with.

I don't know about his explanations though, I don't think they're particularly accurate. and the font and music do nothing to add credence!

Well, like I said, marbles, as in the glass spheres, nope. not a chance.But as far as the spherification or polymer spheres, then thats different. but spherification that large would be nigh impossible (in my opinion).

So insofar as doing what he says, then as Bored Chemist says, the video is 'Bollocks' (best word ever by the way! it doesn't get used enough here is Australia)